need help asap!!! have to bleed it every time i start it!!!
 

i have a 93 cummins and every time i go to start it i have to bleed it, but then runs perfect after. its like fuel is running back into the tank when i let it sit for more than 10 minutes. what holds the prime in the fuel lines???

You probably have a small leak in line letting air in, they often will leak air in without leaking fuel out. :c:

thats what my first thought was...but i went ant rtv'd every single spot where there could possibly be a leak from the tank to the lift pump and made sure every line bolt and fitting was tight... it just seems to me the fuel is just draining back to the tank. i went and tried to prime it manually at the lift pump and the pump ran out of fuel and there wasnt anything left to pump...

I run a check valve just upstream from the VP inlet to avoid this type problem.

i had a leak at my fuel filter housing at the return, which was causing a similiar problem but it was more of an overnight time frame issue.

RTV'd fuel lines :humm::s:

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Good to see a member from the past return :c:

Can't the lift pumps allow fuel to bleed back

It could but the rtv fuel line thing is gheto!!! 86 that shit!! new hose and clamps!!!:tu:

You guys need to go back to the books. Let it sit for a while, don't try n fire it up n see if there's any prime at the LP the diaghram in them often goes bad n will drain fuel back to the tank.

Try bumping the engine a bit to make sure the pump lever is up on the cam.
That's what these forums are for - people who don't have the necessary books and/or experience. Not jackwagon know-it-alls.

Yup and often rusted or cracked fuel lines do the same :c:

Kinda hard when fuel lines on these trucks are hard plastic. besideds I've had 3 1st gens do it to me. always been the lift pump.

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I'm sorry you guys are giving things that are like 1 in a million. the stock 1st gen lift pumps are bad for bleeding back

Oh I see, hard plastic dosn't crack :humm: ....... Especially in the cald weather right ? :moon: Oh no I see since you've had 3 do it out of millions of trucks, thats all it could be :moon::moon:

The lift pump is a very possibly the issue. It could very possibly be an air leak somewhere else but a lift pump is fairly cheap and it probably would not hurt to replace it anyways so it won't leave you stranded i'm the future. That would be the easiest place to start

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And there is no reason to be an a$$ about the guys answer to the problem. Yes he has only had 3 first Gens but that is more than about everybody and by his word this has been his fix to this problem every time. Also the lift pump is a common cause of this symptom...so:moon::moon::moon:

i replaced the LP with an electric fuel pump. it bleeds way faster now and i can prime it before turning it over but it still doesnt start!!!!!!!!!!!!!!!! im going f-ing nuts!!!. every line has band clamps now and no more lift pump. my main fuel screw is leaking a little bit of fuel so how do i get a new o-ring without buying a whole kit for the ve pump?

Well there's your problem. Your fuel screw o-ring is letting air into the injection pump. The reason you can get away with the fuel flowing back with an electric LP is as soon as you turn the key n wait to for the wait to start light to go out the fuel is already back at the injection pump.

OK so I'm supposed to put up with someone being an A$$ to me and not return it :humm::fu::fu::fu:

You seem to know alot about this problem for a guy drives a P-pump and doesn't like VE's.

I only have a p-pump because my VE had a cracked block when I got it. I found two 12v's in my area both sitting next to eachother one was a 93 VE with 330 km KM on it, dirty as could be n BLACK oil. Or the 95 p-pump with a new head n 180 horse injection pump with less mileage and a golden colored oil with 303k KM and it was clean. Plus the guy wanted more money for the VE so I took the p-pump n grew to like it a lot for the topend power it has over my modded out VE. If it wasn't for the VE costing more I'd still be running a VE with 100 horse injectors, timing to the head, maxed pump, turbo, fuel pin, piston lift pump, e-fans exhaust n intake.

I never said I didn't like them just grew past them. I have had 3 trucks all with VE's I'm not stupid when it comes to them.

so i got a new o ring and it seemed to fix the problem...then it sat over night and didnt start again!!!! so i kept looking and the fuel supply line that goes from the filter to the VE pump was leaking a tiny bit where it bolts to the VE pump... maybe it was also sucking in air there too? i took the line off and im getting a new one tomorrow. god i hope this is the final leak to this system.... im tired of it not starting up without a bleed :dang:

:humm: Fuel line leaking :humm: well what do you know.........keep us posted :c:

will do! its leaking at the nut that threads into the pump... it wasnt sealing right. ive spent the past 2 weeks trying to get it to start reliably every time! if this doesnt fix it ill go crazy!

Let me just say this....if its leaking fuel, its more than a 90% chance its sucking air. Thats the reason why when you test things for leaks, you use a regulated air source. Air will find holes that liquids wouldn't think about coming thru.
In these older trucks, if in doubt, replace it. If a fuel line in hard, replace it. If its got dry cracks in it, replace it....
If you see a dry cracked rubber brake line going to your front brakes, you'll replace it, right? Do the same for the fuel lines....
Check valve in the return line is a +.
I replace all the mechanical lift pumps I can get with quality electric pumps. A busted diaphram will pump your crankcase full of diesel. Plus when old, you loose pressure.

A electric pump will prime your filter faster pressurizing your line with the switch being turned on, plus I wire them into a Hobbs Switch. You loose oil pressure, it kills your motor...simple, safe insurance.

Why?

A check valve in the return line should stop air from leaking back into the system if the return line is not submerged in the tank.

Hmmm, interesting. You know injector pop pressures run in the thousands of psi, right?

Have you ever seen an injector taken apart?

Good place for a check valve is about three inches BEFORE the VP inlet.

I used to work at a shop reworking pumps and injectors....25+ years....for diesel trucks and cars.

MMMMM my bad, I did not know the ONLY return line came from the injectors.
And yes I have had injectors apart, put back together and run.

Yea but not on a 1st gen Cummins apparently the only thing that causes a 1st gen to loose prime is the lift pump :w2:

So then, can you please explain how air can get into the system from the return side?

Yea but not on a 1st gen Cummins apparently the only thing that causes a 1st gen to loose prime is the lift pump :w2:
Or sucking air.....

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So then, can you please explain how air can get into the system from the return side?

A old sticky faulty injector can cause it, though its very very
unusual....atmospheric pressure is more than 0, but it can happen. If a injector sticks open for any length of time AFTER POPOFF OCCURS, you can get air.
If air can get into injector lines, why not the returns? Is there some magical law that keeps it safe?

Well I must have an odd ball 12V mine has a Tee in the return line from the injectors and where does that other line on the Tee go, ahh yeah the injection pump.
Must be some after market hot up thingy.

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Motaxraca33, by chance are you keeping an eye on your engine oil level? If it is rising there is a chance you have a bad seal on the input shaft. Not real familiar with this seal but if it leaks fuel it could leak air back into the pump.

Maybe you should put a check valve in there, then!

Must be some gravity/suction drain-back thing. :lol88:

Better yet, you and Screamin Metal boy should team up and submit a fuel system design change to Cummins. Must be some kind of miracle any of them are running at all with this egregious flaw in the fuel return line. :w2:

Well who had razor blades for breakfast then? Very sharp today.
Just pointing out that air does NOT have to flow back past the injectors to get to the injection pump as per the earlier post it has direct access via the bleed line.
Having seen many "impossible" things happen in the mechanical world any thing is possible.
Just trying to give some constructive help to a man in need, may be a bit of a stretch but it may help. Any constructive input?

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  Jul 10, 2012 ... Each fuel injector has a return line cap that is attached with 2 o-rings, and over time these can either leak fuel or suck air....both will cause your ...

There's several instances were you can suck air at the return....just go ahead though and believe what you want to believe....it can even happen to a Cummins....Been there, Done that....


Better yet, you and Screamin Metal boy should team up and submit a fuel system design change to Cummins. Must be some kind of miracle any of them are running at all with this egregious flaw in the fuel return line. :w2:

How did you know I was a Powertrain Engineer at Dodge?

NP,
So what flaw in the Cummins design were you re-engineering when you added a check valve in the delivery line? Fuel can only flow back when something (AIR?) takes it's place. So where was the air coming from in your case?

Can we get back to the OP's truck :s:

Great idea. Too bad we have to waste time barking up the wrong tree. Just to clarify, surely nobody thinks the pump return is an open drain do they? Chime right in now if you still believe a single word about the return should have ever been uttered.

Ok guys... I'm sitting here in the hospital kind of drugged up on pain meds confused at what I'm reading! Lol should I put a check valve in the return line just after the "T"? I have rubber hose there anyways. A local shop has a one way flow check valve for 42 bucks... Would that eliminate any possible drain back and losing prime on the return side? Just to keep fuel at the injectors so hopefully it starts up every time! And I found a tiny leak at one of the compression fittings where i connected the lines together... It didn't start up again after sitting overnight, that's when I found the leak.

Just curious, How did we get from fuel system troubleshooting to drugged up in the hospital?